The present invention relates to weather strips configured to operatively couple to at least one of peripheral edges of panels and peripheral edges of openings in bodies of automobiles. When the panels are in closed positions, the weather strips seal gaps between the panels and the bodies of the automobiles by making elastic contact with the bodies of the automobiles or the panels. The panels include: side doors; back doors, trunk lids; and hoods.
As shown in FIG. 6, a weather strip 10 has been configured to operatively couple to a peripheral edge of a side door 1 of an automobile. When the side door 1 is in a closed position, the weather strip 10 makes elastic contact with a body 2 and seals a gap between the side door 1 and the body 2.
As shown in FIG. 7, the weather strip 10 includes an installation base member 11 and a hollow seal member 12. The installation base member 11 is fit on a frame 1a of the side door 1. The hollow seal member 12 is integrally molded with the installation base member 11 and is configured to make elastic contact with a peripheral edge of an opening in the body 2 of the automobile when the side door 1 is in the closed position. The hollow seal member 12 generally includes EPDM sponge rubber having specific gravity that falls within a range of 0.35 to 0.65 in consideration of flexibility, weather resistance, extension, and rigidity.
In order for the hollow seal member 12 to make elastic contact with the body 2 when the side door 1 is in the closed position, the weather strip 10 is required to perform an improved deformation followability. Also, in order to prevent entrance of water, wind, dust, and noise from outside, the weather strip 10 is required to perform a sealing function. The sealing function is an airtight condition formed by a reaction, from the weather strip 10, of a degree equivalent to closure of the side door 1. The sealing function of the weather strip 10 is checked by adjusting compression load value (value measured by a test of compressing, bending, and deforming the hollow seal member 12 in a pressing and deforming direction at a speed of 20 mm/min), which is a general evaluation index for the weather strip 10.
As the reaction of the weather strip 10 increases, force for closing the side door 1 is increased. As a result, door closability is degraded, that is the door becomes hard to close.
In this connection, in order to improve the door closability of the weather strips on the panels, lowering the compression load value has been the sole solution. The solution includes partially reducing the hollow seal member 12 in thickness and employing materials low in specific gravity or elasticity as the hollow seal member 12 (see, Japanese unexamined Patent Publication No. 2011-183935 and Japanese examined Patent Publication No. 5587062).
Unfortunately, however, the hollow seal member 12, which is partially reduced in thickness or which includes the materials low in the specific gravity or the elasticity, is decreased in sealing surface pressure and degrades the sealing function including water cut off function of the weather strip 10 when the side door 1 is fully closed, in the closed position in other words.
This is caused by the fact that the compression load value has been believed to include only static reaction of the hollow seal member 12 and dynamic reaction of the hollow seal member 12 has not been taken into consideration.
More specifically, impact elasticity of rubber includes the static reaction and the dynamic reaction. The “static” and “dynamic” indicate speed for compression. The “static” indicates movement at a very low speed or even without speed at the time of compression. The “dynamic” indicates movement at a very high speed at the time of compression. The “static” affects the sealing function when the door is in the closed position. The “dynamic” affects the door closability when closing the door.
Difference in the compression load value depending on difference in the speed has been overlooked and has not been argued about. As shown in FIG. 8, when a hollow object, including rubber-like elastic body such as rubber, is compressed and movement of compression is stopped at a fixed compression amount, reaction of the hollow object temporarily jumps up to the maximum value at first, and then lowers to a stable value with the passage of time. The reaction in total (30+40) includes: reaction (30) relative to the static compression; and reaction (40) relative to the dynamic compression. The reaction (40) relative to the dynamic compression indicates viscosity of material. The static compression is a condition under the stable compression amount without movement for the compression. The dynamic compression is a condition in which the compression amount changes at the high speed.
In order to improve door closability, more specifically as means to close the door with a low energy, the inventors of the present invention considered bringing the viscosity (loss elastic modulus: performance for converting kinetic energy into thermal energy) of the material essentially identical to zero.
As the value “40”, which indicates the viscosity of the material forming the hollow seal member 12 decreases, the compression load value does not vary under the static compression or the dynamic compression. Accordingly, it is possible to lower dynamic compression load when closing the door, while maintaining static sealing surface pressure, in other words while keeping the sealing function (including water cut off function) high when the door is in the closed position.
Japanese unexamined Patent Publication No. 2011-183935 and Japanese examined Patent Publication No. 5587062 aim at preventing degradation in the door closability but do not teach or suggest the loss elastic modulus, which affects the door closability. The loss elastic modulus indicates the viscosity of the material forming the hollow seal member.
Accordingly, an object of the present invention is to provide the weather strips improved in the door closability by laying emphasis on the viscosity of the material of the rubber-like elastic body.